Injection molding is a technology commonly used for high-volume manufacturing of parts made of meltable materials, most commonly of parts made of plastic. During any injection molding process, typically a melted (plasticized) resin, such as a plastic resin in the form of small beads, is forcefully injected into one or more mold cavity having a particular cavity shape. The injected plastic is held under pressure in the mold cavity, cooled, and then removed as a solidified part having a shape that essentially duplicates the cavity shape of the mold. The mold itself may have a single cavity or multiple cavities. Each cavity may be connected to a flow channel, called a runner, that directs the flow of the melted plastic though a feed gate and into the cavity. Thus, a typical injection molding cycle may comprise three basic operations: (1) heating the plastic in an injection unit to allow it to flow under pressure; (2) injecting the melted plastic into a mold cavity or cavities defined between two mold halves that have been closed and allowing the plastic to harden (cool) in the cavity or cavities while under pressure; and (3) opening the mold halves to cause the part to be ejected from the mold. A continuous molding process may comprise two or more injection molding cycles.
The two mold halves of an injection molding system typically are held together by machinery such as a hydraulic press. Generally connected to each mold half one or more molding face. Each mold face may be described, for example, as either a cavity plate or a core plate. The cavity plate may have defined in its surface one or more depressions in the shape of a top surface of a part to be molded. The core plate may have defined in its surface one or more protrusions, each corresponding to a depression in the cavity plate, in the shape of a bottom surface of a part to be molded. The depressions and protrusions are geometrically configured such that, when the two mold halves are brought together, the protrusions in the core plate extend into the depressions in the cavity plate so as to define a cavity between the cavity plate and the core plate. The number of cavities defined one or more pair of molding faces between a pair of mold halves shall be referred to as the “maximum cavitation” of the mold. The maximum cavitation of the mold also represents the maximum number of parts that can be produced per cycling of the two mold halves.
Injection molding systems also may be stacked, such that for any given cycle of the injection molding press, a plurality of pairs of molding faces are pressed together between the two mold halves simultaneously. For any given injection molding system, the number of pairs of molding faces operating at any stage or cycle during a continuous molding process to produce parts shall be referred to as the “face number” of the system, which alternatively may be represented using terms such as “single-face,” “double-face,” “6-face,” or even “multi-face,” for example.
An injection molding system can represent a large capital investment on the part of a manufacturer, in that complex machinery and control systems must be designed and installed to fulfill operational requirements, particularly with respect to production capacity. For example, injection molding systems may comprise as standard components the molding press itself, an injection screw, a mold mounting block, a heater, a cooling system, an ejector system, a hot runner system, a water connection, an air connection, a hydraulic connection, a limit switch connection, a basic insert connection, and a plug configuration box. These standard components represent the necessary capital investment even before a mold face can be designed, fabricated, installed, optimized, and placed into operation.
The disadvantage of high capital cost of an injection molding system is typically coupled with a disadvantageously limited flexibility of an established system. For example, systems are generally tailored specifically to operate with a set cavitation, with molds designed for one particular part, such that any change of the system may require either significant retooling or even complete rebuilding of the system. The molding press itself may have been designed to occupy a certain amount of floor space, and the halves of the mold press may have been configured to open only to a certain set width. These become critical issues for manufacturers whose volume of business may expand or contract significantly over any given period of time.
As a further illustration, consider a manufacturer who has invested in a single-face injection molding system with a cavitation of eight. If the manufacturer's business outgrows the capacity of this system, it is nearly impossible to convert the system to a single-face system with a cavitation of sixteen or to double-face system with two molds of cavitation eight, so as to double the maximum production volume. Thus, the manufacturer is forced to purchase a complete new system including all of the standard components. In one scenario, the manufacturer might purchase a new system identical to the old to avoid the technical risk of scaling the old system up or down to produce the new system. If demand for the product has not necessitated the resulting 100% increase in capacity, one of the systems will not be used to its full capacity for some time. But even if the 100% increase has occurred, two identical systems will be operating side by side with duplicated standard components and double the maintenance costs. In another scenario, the manufacturer might purchase a new system with double the capacity of the old system. Here, the old system may be scrapped, sold at a substantial loss, allowed to lie dormant, or at least be underused unless and until the demand for the manufacturer's product has increased another 50% to require the combined output of the old system and the new system. Even when demand does increase to that level, standard components will be duplicated.
Thus, there exists a need for scalable injection molding systems that can reduce wasted capital and maintenance expenditures on duplicated standard system components.